The present invention relates to a retortable pouch and a packaging material for the retortable pouch in which cooked food is sealed and preserved.
In general, a retortable pouch is required to be made of a material impermeable to gas in order to ensure good preservation of cooked food packaged therein. Accordingly, a laminated film consisting of a polyester film, an aluminum foil and an inelastic polypropylene is generally used as a retortable pouch.
When cooked food packaged in a retortable pouch made of the above laminated film is heated in boiling water, it requires a long time to restore the food to its original condition. Therefore, a new method in which cooked food packaged in the retortable pouch is heated by the use of a microwave oven in a few minutes has been proposed. However, since microwaves generated by a magnetron are intercepted by the aluminum foil of the laminated film, cooked food packaged in the retortable pouch cannot be heated adequately.
Furthermore, sparks are generated at some parts of the retortable pouch which are irradiated by the microwaves.
That is, when the retortable pouch made of the above laminated film is used for packaging cooked food, the cooked food packaged therein cannot be heated adequately by a microwave oven.